imb- (Old Irish) comes from Proto-Celtic ambi-, from Proto-Indo-European h₂m̥bʰi, from Proto-Indo-European h₂n̥tbʰi, from Proto-Indo-European h₂énts, from Proto-Indo-European h₂ent-, from Proto-Indo-European h₂en- — on, onto.
imb- (Old Irish): around, about